1. Field of the Invention
This invention relates to a vehicle obstacle detecting system, more particularly to a vehicle obstacle detecting system which has a combination of two kinds of detectors or sensors for detecting an obstacle present ahead on the course of travel of the vehicle.
2. Description of the Related Art
It has hitherto been proposed mounting a laser radar (also known as "lidar"; which emits a laser beam [electromagnetic wave]) or a millimeter-wave radar (which emits a millimeter-wave; an electromagnetic wave of a wavelength different (larger) than the wavelength of the electromagnetic wave emitted by the laser radar) to detect or recognize an obstacle (such as another vehicle present ahead of the vehicle) and based on the result of detection, operating a braking system to decelerate or alerting the vehicle operator. Japanese Laid-open Patent Application Hei 4(1992)-248489 discloses the use of the laser radar. Japanese Laid-open Patent Applications Hei 7(1995)-63842 and Hei 8(1996)-94749 disclose the use of the millimeter-wave radar.
In such a technique, it is necessary to detect or recognize an obstacle present on the course of travel accurately to obtain information such as positional information thereof precisely. However, it is difficult to utilize a detector of a sufficient performance because of, for example, reasons of cost or expense. Conceivably, different kinds of detectors such as the laser radar and the millimeter-wave radar can be used in combination to improve the detection reliability.
When using different kinds of detectors in combination, however, no prior technique has established how to fuse or unify the information obtained from the detectors. In particular, no prior art teaches how to cope with the situation wherein the performance of one of the detectors becomes degraded.